Cartons or boxes are typically delivered to the user flat and formed with fold lines that permit them easily to be erected into the desired rectangularly parallepipedal shape. In a standard box-erecting apparatus the flat boxes are held in a stack in a magazine from which they are pulled one at a time by a suction grab. An unfolder engages another panel of the box and erects it, and the erected box is deposited in a respective cell of a conveyor that itself comprises a top rail, a bottom rail, and a succession of cell-defining elements that move along between and parallel to the rails. A filling apparatus downstream of the box-erecting system loads the necessary contents into the boxes in the cells, and other devices may be provided to fold in end flaps and seal the boxes.
As described in German patent document 2,923,909 filed Jun. 13, 1979 by Otto Weller and U.S. Pat. No. 5,067,937 of H. Aschaber such an apparatus has a support wheel for the grab and for the unfolder. A parallelogrammatic linkage carries these elements so that even though the wheel moves continuously, the grab's angular movement can be temporarily canceled out for the necessary pickup transfer during which the grab effectively is moved only radially inward on the wheel. Once picked up the box is brought up to the peripheral speed of the wheel as it is erected and is then passed off to the conveyor whose transport speed is equal to the wheel's peripheral speed. Once the erected box is set in its cell in the conveyor, the suction grab releases it and this grab retracts radially back into the wheel, out of the way, while the unfolder is moved back to its starting position.
The supply magazine holds the cartons normally on edge with the frontmost carton, that is the carton on the end of the stack that is picked off by the grab, lying in a plane which forms an angle, herein termed the pickup angle, with the plane in which the grab moves as it contacts and clings to the frontmost carton. The pickup angle is a small acute angle that ensures that the grab engages solidly against the frontmost carton before it pulls it from the stack.
Such a machine is built to work on cartons of different dimensions so that the magazine is adjustable to hold the differently sized flattened cartons. When carton size is changed it is also necessary to adjust the vertical position of the grab relative to the conveyor underneath it. Hence it is also essential to adjust the position of the magazine relative to the grab. To ensure that the grab engages the cartons at the right location the supply magazine is moved vertically to the desired position relative to the grab. Then the magazine must be repositioned horizontally relative to the grab so that the grab will engage the frontmost carton with a force that is sufficient to stick to it but not so large that it displaces the entire stack of cartons or damages the cartons or grab.
This complicated setup whenever carton size is changed is an onerous process.